 We talked about slope.  We talked about positive and negative slope.  We talked about how to find slope and the x and y intercepts.

 Correlation is how two variables are related.  The purpose of doing correlations is to allow us to make a prediction about one variable based on what we know about another variable.  For example, there is a correlation between income and education. We find that people with higher income have more years of education. ◦ If we know a group’s income, we can predict their years of education.

 In a positive correlation, as the values of one of the variables increase, the values of the second variable also increase.  The example about income and education is a positive correlation. People with higher incomes tend to have more years of education. People with fewer years of education tend to have lower income.

 SAT scores and college achievement—among college students, those with higher SAT scores also have higher grades  Happiness and helpfulness—as people’s happiness level increases, so does their helpfulness

 In a negative correlation, as the values of one of the variables increase, the values of the second variable decrease.  An example is the correlation between TV viewing and class grades—students who spend more time watching TV tend to have lower grades (or phrased as students with higher grades tend to spend less time watching TV).

 Education and years in jail—people who have more years of education tend to have fewer years in jail (or phrased as people with more years in jail tend to have fewer years of education)  Crying and being held—among babies, those who are held more tend to cry less (or phrased as babies who are held less tend to cry more)

 There is no relationship between the two variables.  No connection between the two can be found.  Examples: ◦ How fast a person runs and the amount of stars you can see in the sky at night. ◦ The height of a person and what cereal they like.

 Continuous motion between points on a graph.  There are no breaks in the graph.  Any value of x will give us a corresponding value of y.  We could continue the graph in the negative and positive directions, and we would never need to take the pencil off the paper.  Examples: ◦ Your body temperature over a 24-hour period. ◦ Wind speed over a 24-hour period ◦ The height of an airplane above the ground as it travels from New York to Washington, DC.

 Not continuous. (discontinuous)  Breaks or holes in the graph.  Not every value of x will give us a corresponding value of y.  We will have to pick up our pencil in order to continue the graph.  Examples: ◦ How many people go to the movies for a week. ◦ The number of books checked out of the library each day for a month.